Control of modern gas turbine engines oftentimes relies upon sensing certain critical operational parameters of the engine, such as a high temperature, high volume gas flow driving the energy extracting turbine blading. It is desirable that sensing apparatus such as thermocouples measuring the temperature at locations within turbine interstages be readily accessible and removable for maintenance and/or replacement purposes. Yet the relatively complex internal geometry of the gas turbine engine, coupled with pressure differentials and extensive variations in thermal response of the various support structure within the engine, conventionally results in emplacement of the thermocouple at a location deeply imbedded within the engine housing structure wherein maintenance and/or replacement requires significant disassembly and reassembly of the overall engine.